vipernicus42

iTrader: (4)

Hey All,

Well I've developed some annoying carb problems! They've been slowly building for some time and I've tried lightly to fix them and eliminate other possibilities, but this morning they got so bad that I just had to post.

Basic Summary: At "idle" (choke out, fast idle rod connected is the only way it runs without dying), gas is not only *visibly* gushing into the primaries, but it's dripping out one of the secondaries as well! (the one closest to the firewall).

I've replaced the needles and seats twice now attempting to remedy the problem and checked the float drop. I never tried adjusting it because the float drop has been perfect since the day Sterling gave it to me, I just keep checking to make sure!

I've made sure my fuel pressure is dead-on with my ReSpeed fuel pressure guage. I have tried both 2.5psi and 3psi just to see if it would make a difference.

Sometimes the carb behaves, and I can drive around with relatively few problems, but most of the time it spews too much gas and chokes it out. This is the first time it's ever come out in one of the secondary barrels, but it's not uncommon for me to see it gushing out the primaries.

My carb is a new Sterling, I got it this spring, and the only change that has been made to it at all is the primary slow air bleeds, a change which Sterling himself made on the carb while I was at his place. I know the reasoning behind the change, and I've even tried changing it back to stock primary slow air bleeds, to no avail.

What could cause it to flood so badly? It's almost like my primary air bleeds are blocked off and it's syphoning fuel from the bowls, but I checked them and they're clear.

And I've banged on those fuel bolts so many times that the powdercoat is wearing off the top! (in an attempt to get the needles to re-seat if that's the problem.

Any suggestions?

Jon

Edit: I just want this to be abundantly clear : The Sterling Carb and the workmanship of Sterling and Carl are not being questioned here. This is the second Sterling I've had, the first never EVER gave me any problems, and this one has only been flaky as of late. I don't want anyone coming in here telling me to ditch the carb, telling me to switch the carb, or taking shots at the guys.

MosesX605

I dunno. How does the carb feel during light/heavy acceleration?

Hopefully RX7Carl or Sterling will pop in with some advice.

t_g_farrell

iTrader: (1)

Stupid question; why do you need the choke on all the time to idle ? Did your previous Sterling require this as well ? Maybe part of the problem is the choke circuit making it rich. Otherwise it sounds like a stuck float or valve.

vipernicus42

iTrader: (4)

Most sterlings don't even come with the fast idle rod attached at all, I specifically requested it on mine. The rest of the choke assembly has been removed though.

The reason I have to keep the choke out to keep it running is because at low (idle) speeds the engine gets way too much gas and not enough air, vaporizaiton doesn't happen, and the engine floods out and dies.

When I pull my choke **** out it pulls on the arm that lowers the fast idle rod, bringing the engine up near 2krpms... where it won't choke out due to the excess gas.

Jon

t_g_farrell

iTrader: (1)

So what happened with the first Sterling you mentioned. Did it have problems as well ?

To me it sounds like a jet or adjustment issue. The idle circuit is too rich it seems. Is your enigne stock ?

vipernicus42

iTrader: (4)

Engine is bone stock 12a.

The first Sterling was zinc coated.. as soon as I heard that they did powdercoating (and manifold porting) I sent mine back down so I could get a powdercoated one with a ported and powdercoated matching manifold.

That Sterling ran better than any carb I have ever had the pleasure to drive, period!

The only reason I say "that sterling" and "this sterling" is because I know that they actually are two different carbs... we pretty much cross-shipped the two carbs (or at least that's what the plan was). I don't think there are many, if any, internal differences. I know mine was an earlier version, one of the first, and this one is more recent, but from my discussions with Sterling and Carl, the changes aren't anything that would lead to these kinds of problems.

Jon

vipernicus42

iTrader: (4)

It's not just that it's too rich... there's gas dripping into one of the secondary barrels when the car's sitting with no load at 2krpm!

That's definitely not supposed to happen!

As for the primaries, jetting doesn't explain why it *sometimes* runs fine and will idle, and the rest of the time inisists on dumping raw gas into the barrels.

Though once I figure this problem out, you're right it was running a *little* rich at idle on purpose, de-tuned if you will to give me a baseline to start with. I still have to jet it. Jets/bleeds are ordered and on their way.

Jon

vipernicus42

iTrader: (4)

Hey Guys,

I went out at lunch, popped the top off the carb, open and closed the floats about a dozen times each, then put the top back on and boom, it idles.

So either some crud got stuck between the needle and seat, or the needles and seats are just taking their damn time to wear into each other.

However, it still doesn't explain why it stalls when I come down from speed, or why it chokes on right-hand turns.

Jon

t_g_farrell

iTrader: (1)

Maybe it's a vacuum leak thats causing your problems. The reason I say this is that you mentioned it seems like the primary air bleeds are blocked off ( causing richness ) and that it just started happening. Maybe something vibrated loose on the carb or a connection to the manifold. We know your already borderline rich anyway because of the choke being on.

t_g_farrell

iTrader: (1)

If it was a Dellorto I could explain both

Is your fuel filter working ? How did crud get in there ?

vipernicus42

iTrader: (4)

I'm not boarderline rich because of the choke.... there is no choke assembly, it has been removed. The only thing left is the fast idle rod. When I pull the choke **** out it's the equivalent of holding your foot on the gas pedal to crack open the primary butterflies to the tune of 2krpm.

Could still be vac leak related tho I s'pose.

And as for the crud.... well I left my gas cap in New York and the parts store has taken more than 2 months to get me my new one!

Jon

bstrange99

Make sure you have +12v going to the return solenoid, otherwise, regardless of float level, fuel will dump into the venturi's, rather than returning to the tank.

MattG

iTrader: (2)

On the Sterling carb, they removed the Solenoid that controls that so it no longer needs to be pluged into a power source.

cdrad51

I doubt a sterling carb has a return solenoid, but maybe my memory fails me.

edit: haha you beat me Mattg, maybe my memory didn't fail me after all.

MattG

iTrader: (2)

Always go with your first instict! lol

The return soleniod just opens to let the fuel vapor out into the charcoal canister when the engine is not in use, becuase when the engine is in use, it just sucks the vapors back down into the motor.

rmriggin

does your manifold still have the decel valve? Maybe the decel valve is stuck, that could explain the problems when slowing down.

DavidMyers53

I think you're talking about the air vent or bowl vent solenoid. I've be having all kinds of problems because of mine. What it would usually do is if the fuel pump was on and the motor wasn't running, gas would leak out of the jets and fill up the engine. I finally removed the solenoid from the carburator, and found the next problem, which was crud in the float bowls from the crud in my gas tank (car had been sitting for 13 years). It caused similar symptoms, just not as bad as before. After cleaning this out, it is running much better. The fuel filter is still picking up crud from the gas tank, even after having it boiled out at a radiator shop, so I change filters frequently. I also added a secondary filter at the carburator so I can see if I have fuel flow or not, and a remote fuel pump cut-off switch to help with deflooding procedure.

- David

cdrad51

So a right hand turn would make the fuel level higher on the primaries side and lower on the secondaries side. Hmm. I wonder whether that bucking comes from too much or too little fuel.

Kentetsu

You say it chokes out on right hand turns? That's interesting, are you sure you don't mean left hand turns? The reason I ask is because I had an issue with flooding out on left turns, which turned out to be too high of a fuel pressure setting. Is there any chance that your fuel pressure gauge could be faulty?

vipernicus42

iTrader: (4)

Fuel Bowl Vent Solonoid is removed on all Sterling carbs. Aparently it's a royal pain in the *** to remove it properly, but they do it. So that's definitely not the source of my headaches. Good guess though.

As for the deceleration valve.... well the vacuum-pot that operates it was removed, and the holes jbwelded shut, but I left the butterfly and rod in there. I did that because I was told that since the opening of the runner was shaped with the rod and butterfly in mind, simply removing it would disrupt airflow a little. I JBWelded the arm so that the butterfly stayed straight up and down but I'll check to make sure it has not changed.

Keep 'em comin' guys!

Jon

vipernicus42

iTrader: (4)

Nope, it is very CLEARLY right hand turns only.

FPR has been replaced, max it will allow pressure is 4psi. I never had the right hand turn problem back when I was running 4.5psi on the old (read:wrong) regulator.

I'm doubtful the guage is faulty. Even if it wasn't a quality guage, the fact that what the guage shows corresponds to what I do to the regulator (max 4psi, min 1psi) tells me it must be in the ballpark.

Honestly I'm thinkin' more and more that the shutter valve theory is the most ingenius idea I've heard so far. It seems to make sense that if my JBWeld of the rod didn't hold, the butterfly would flap shut on low speed right turns... I'll have to check it out. Again, another problem/possibility which will not be there once I get my ported manifold!

Jon